Phase imaging techniques, which allow for quantifying optical phase delays experienced by light interacting with matter, have received increasing interest over the past decade, particularly in the context of biological imaging used to define morphology and dynamics of live cells. Various single-point and full-field techniques have been developed, including optical coherence tomography (OCT) and phase-contrast OCT (PC-OCT, used to quantify phase retardation in biological samples), Fourier phase microscopy (FPM, utilizing the scattered and unscattered light from the object as the object and reference fields in an interferometer), Hilbert phase microscopy (HPM, allowing to obtain phase images from only one spatial interferogram recording), and diffraction phase microscopy (that combines the single-shot feature of HPM with the common-path geometry of FPM). See, e.g., G. Popescu, “Quantitative phase imaging and application: a review” (2006, available at http://light.ece.uiuc.edu/QPI_review.htm). Polarization-sensitive versions have been demonstrated for some of the foregoing techniques.
Polarization-sensitive phase imaging techniques generally allow for detection of changes in the polarization state of light as it interacts with the sample. Such techniques may improve imaging contrast. In prior art, polarization information has been processed and presented by utilizing the well-known Stokes vector and Mueller matrix. The Stokes-Mueller formalism is based on the intensity of polarized light transmitted through a sample as a function of the polarization state of the incident light. It has been assumed that an intensity-based approach provides all the information necessary for analyzing a material, and thus the Stokes-Mueller formalism naturally lends itself as an algorithm for analyzing the images. See, e.g., M. Mujat, “Polarimetric characterization of random electromagnetic beams and applications,” University of Central Florida, 2004, for a review.